Helical rod guide and method

ABSTRACT

A rod guide  10  for positioning on a sucker rod includes a sleeve-shaped guide body  12  and two or more spiraling vanes  14, 16  each extending radially outward from the sleeve-shaped body, with each vane spiraling about the body and defining a flow path between circumferentially spaced vanes. Each vane has a forward portion  24  spiraling in a forward direction, and a backward portion  26  spiraling in a backward direction rotatably opposite the forward direction. The rod guide may be used for either reciprocating rod or rotating rod applications.

FIELD OF THE INVENTION

The present invention relates to rod guides and scrapers supported on asucker rod for removing debris from the interior wall of productiontubing and protecting the tubing and sucker rod couplings from excessivewear. More particularly, the present invention relates to a rod guide orscraper with vanes spiraling along the length of the guide and fluidflow channels between the one or more vanes, and to a method of moldingsuch a rod guide.

BACKGROUND OF THE INVENTION

Various types of rod guides and scrapers have been devised to removewax, paraffin, and other debris from the interior wall of productiontubing. Most rod guides include a sleeve-shaped body for positioningover the sucker rod and one or more vanes projecting radially from thebody, with one or more vanes being relatively straight (parallel to theaxis of the rod), slanted (inclined at an angle relative to the axis ofthe rod), or helical (spiraling relative to the axis of the rod). Thespacing between the vanes, or between a slanted or spiraling singlevane, serves as a flow path for passing production fluid past the rodguide.

Most rod guides today are manufactured from a plastic material. Rodguides may be secured in various ways to the sucker rod. In oneapplication, the rod guide is molded onto the sucker rod, and is thusrigid with the sucker rod due to the molding process.

For many applications, a rod guide provided with spiraling vanes ispreferred over a straight or slanted vane guide, since more of thecircumference of the tubing may be cleaned by a single spiraling guidecompared to a single straight-vane guide in a reciprocating rodapplication. Spiraling rod guides do, however, cause high fluid dragforces to fluid passing by the rod guide and to the surface.

U.S. Pat. No. 5,277,254 discloses a helical rod guide for use with aprogressing cavity pump rod. The helical guide may employ either one ortwo lead vanes. U.S. Pat. No. 6,182,754 discloses a helical scraper fora reciprocating sucker rod. Each of two vanes extends 180° about thebody, with the ends of a flow channel between the vanes being parallelto the body of the sucker rod. U.S. Pat. No. 6,439,311 discloses amethod of retarding sand buildup by employing helical vanes which areaffixed to connective rods by shrink couplings. Other patents ofinterest include U.S. Pat. Nos. 5,660,534, 5,941,312, 6,065,537,6,290,475, and 6,484,882, and Canadian Patents 2,260,710 and 2,291,394.

The disadvantages of the prior art are overcome by the presentinvention, and an improved rod guide and method of molding a rod guideare hereinafter disclosed.

SUMMARY OF THE INVENTION

In one embodiment, the rod guide for positioning on a sucker rodincludes a sleeve-shaped guide body and two or more vanes each extendingradially outward from the sleeve-shaped body. Each vane spirals aboutthe body and defines a flow path between circumferentially spaced vanes.Each vane has a forward portion spiraling in a forward direction, and abackward portion spiraling in a backward direction rotatably oppositethe forward direction.

In one embodiment, the rod guide includes a plastic materialsleeve-shaped guide body, and the forward and backward portions meetadjacent a middle region of the guide body to form an axially elongateand continuous vane. The rod guide may be molded by engaging first andsecond molds to form a radially inner chamber within the engaged moldsto define a sleeve-shaped guide body, with the first and second moldsforming a radially outer chamber extending radially outward from and incommunication with the inner chamber and defining one or more spiralvanes. Each vane has a forward portion spiraling in a forward directionand a backward portion spiraling in a backward direction rotatablyopposite the forward direction.

These and further features and advantages of the present invention willbecome apparent from the following detailed description, whereinreference is made to the figures in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial view of a suitable rod guide molded on a suckerrod.

FIG. 2 is another view of the rod guide shown in FIG. 1.

FIG. 3 is a canted top view of the rod guide shown in FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts a plastic material rod guide 10 according to thisinvention. Referring briefly to FIG. 3, the rod guide 10 includes agenerally sleeve-shaped guide body 12 for positioning on a sucker rod,and two or more vanes 14, 16 each extending radially outward from thesleeve-shaped body 12, with each vane spiraling about the guide body anddefining a fluid flow path 18, 20 between circumferentially spacedvanes. As shown in FIG. 1, the rod guide may be of a molded one-piececonstruction fixed to a rod 22 during the molding process, in which casethe rod guide is well suited for use with a reciprocating rod to cleanthe interior of production tubing. If desired, a sucker rod rotator maybe used to slowly rotate the sucker rod and thus the guide 10 withrespect to the tubing string during use. In another embodiment, the rodguide 10 may be mounted on the sucker rod 10, which rotates to drive aprogressive cavity pump, with the rotating rod guide engaging theinterior of the tubing string.

As shown in FIG. 1, each vane has a forward portion 24 spiraling in aforward direction, and a backward portion 26 spiraling in a backwarddirection rotatably opposite the forward direction. The terms “forward”and “backward” are not intended to be indicative of direction, and onlyindicate that one portion of the vane spirals in a rotatably oppositedirection from the other portion. Looking at the rod guide shown inFIGS. 1 and moving downward along the guide, the forward portion may bethe clockwise direction and the backward portion the counterclockwisedirection, but the forward portion could alternatively be thecounterclockwise direction and the backward portion the clockwisedirection.

Referring still to FIG. 1, the forward and backward portions 24, 26 eachmeet adjacent a middle region of the guide body to form an axiallyelongate and continuous vane, and in the disclosed embodiment theseportions meet at substantially an axial center of the sleeve-shapedbody. In order to minimize the flow losses of fluid passing by the rodguide and between the vanes, the forward and backward portions aresubstantially mirror images of one another and have substantially thesame spiral taper and substantially the same axial length. Each end 28,30 of each vane is tapered radially inward toward the sleeve-shapedguide body, as shown. The end, 28, 30 may define side surfaces extendingradially inward toward the center of the guide in a direction movingaxially toward the extreme end of the guide, thereby facilitatingmolding of the guide.

In a preferred embodiment, each vane 14, 16 has a left-side surface 32as shown in FIG. 2, a right-side surface 34 which is substantiallyparallel to the left-side surface of a respective vane, and the radiallyexterior surface 36 which extends between the left-side and theright-side surfaces. Each of these surfaces is a substantially curvedplanar surface, and each vane has a circumferential width of from 30° to60°. Each vane also extends circumferentially about the guide body from130° to 220° to provide a substantial circumferential area for cleaningthe production tubing string while retaining a relatively large flowarea for fluid passage by the rod guide.

By providing the rod guide with both a forward spiraling portion and abackward spiraling portion, fluid drag through the rod guide isminimized compared to an embodiment which continued to spiral the vanesalong the length of the guide in a single direction. Also, a roundedtransition region 38 is provided between the forward directed portionand the backward directed portion of each vane and further reduces fluiddrag. A circumferential width of each flow passage is from about 120° toabout 150°.

Although the rod guide as disclosed herein is well suited for use on areciprocating rod string, the rod guide may also be used on a rotatingrod string for driving a PC pump. For this latter application, the guidemay be fixedly molded to the rod string as for the reciprocating rodapplication. The guide provides a large bearing area, which is theexterior surface of the vanes, for engaging the interior of the tubingstring to provide for long life. Although the guide as disclosed hereinfor preferred applications may have two generally radially opposingvanes, the guide may be provided with one or more vanes, with each vanehaving a forward portion spiraling in a forward direction and a backwardportion spiraling in a backward direction rotatably opposite the forwarddirection. If three or more vanes are provided, each of the vanes wouldgenerally be positioned at consistent intervals about the circumferenceof the sleeve-shaped guide body, so that three vanes would be spaced atsubstantially 120° intervals.

The rod guide may be molded for fixing on a sucker rod utilizing firstand second molds which engage to form a radially inner chamber in theengaged molds defining the sleeve-shaped guide body. The first andsecond molds may also form a radially outer chamber extending radiallyoutward from and in communication with the inner chamber, and define theone or more spiraling vanes each having a forward portion spiraling in aforward direction and a backward portion spiraling in a backwarddirection rotatably opposite the forward direction.

Although specific embodiments of the invention have been describedherein in some detail, this has been done solely for the purposes ofexplaining the various aspects of the invention, and is not intended tolimit the scope of the invention as defined in the claims which follow.Those skilled in the art will understand that the embodiment shown anddescribed is exemplary, and various other substitutions, alterations andmodifications, including but not limited to those design alternativesspecifically discussed herein, may be made in the practice of theinvention without departing from its scope.

1. A rod guide for positioning on a sucker rod, comprising: asleeve-shaped guide body for positioning about the sucker rod; two ormore vanes each extending radially outward from the sleeve-shaped guidebody, each vane spiraling about the guide body and defining a flow pathbetween circumferentially spaced vanes; and each vane having a forwardportion spiraling in a forward direction, and a backward portionspiraling in a backward direction rotatably opposite the forwarddirection.
 2. A rod guide as defined in claim 1, wherein the forward-and backward portions of each vane meet to form an axially elongate andcontinuous vane.
 3. A rod guide as defined in claim 1, wherein theforward and backward portions of each vane meet adjacent a middle regionof the guide body.
 4. A rod guide as defined in claim 3, wherein theforward and backward portions of each vane meet at substantially anaxial center of the sleeve-shaped guide body.
 5. A rod guide as definedin claim 1, wherein an end of each vane is tapered radially inwardtoward the sleeve-shaped guide body.
 6. A rod guide as defined in claim1, wherein each vane extends circumferentially about the guide body from130° to 220°.
 7. A rod guide as defined in claim 1, further comprising:a rounded transition region between the forward directed portion and thebackward directed portion of each vane.
 8. A rod guide as defined inclaim 1, wherein the rod guide is fabricated from plastic.
 9. A rodguide as defined in claim 1, wherein the rod guide is molded onto thesucker rod.
 10. A rod guide as defined in claim 1, wherein each vane hasa circumferential width of from 30 to 60°.
 11. A rod guide as defined inclaim 1, wherein each of a left side, a right side, and a radiallyexterior surfaces of each vane form a substantially curved planarsurface.
 12. A rod guide for positioning on a sucker rod, comprising: aplastic material sleeve-shaped guide body for positioning about thesucker rod; one or more plastic material vanes extending radiallyoutward from the sleeve-shaped guide body, each vane spiraling about thebody and defining a flow path between circumferentially spaced from theone or more vanes; and each vane having a forward portion spiraling in aforward direction, and a backward portion spiraling in a backwarddirection rotatably opposite the forward direction, the forward andbackward portions meeting to form an axially elongate and continuousvane.
 13. A rod guide as defined in claim 12, wherein the forward andbackward portions of each vane meet adjacent a middle region of theguide body.
 14. A rod guide as defined in claim 12, wherein an end ofeach vane is tapered radially inward toward the guide body.
 15. A rodguide as defined in claim 12, wherein the rod guide is molded onto thesucker rod.
 16. A rod guide as defined in claim 12, wherein the suckerrod is reciprocated within a tubing string, such that a radiallyexterior surface of each vane slides along an interior surface of thetubing string.
 17. A rod guide as defined in claim 12, wherein thesucker rod is rotated within a tubing string, such that a radialexternal surface of each vane rotatably engages an interior surface ofthe tubing string.
 18. A rod guide for positioning on a sucker rod,comprising: a sleeve-shaped guide body for positioning about the suckerrod; two or more plastic material vanes each extending radially outwardfrom the sleeve-shaped guide body, each vane spiraling about the guidebody and defining a flow path between circumferentially spaced vanes;each vane having a forward portion spiraling in a forward direction, anda backward portion spiraling in a backward direction rotatably oppositethe forward direction; and wherein each vane extends circumferentiallyabout the guide body from 130° to 220°.
 19. A rod guide as defined inclaim 18, wherein each vane has a circumferential width of from 30 to60°.
 20. A rod guide as defined in claim 18, further comprising: arounded transition region between the forward directed portion and thebackward directed portion of each vane.